Super-enhancers modulate interleukin-6 expression and function in cancers

Abstract

Background: It is widely accepted that inflammatory cytokine, interleukin 6 (IL-6), was not only elevated in cancer but also important in carcinogenesis. But how did IL-6 be produced in tumor microenvironment remains to be addressed. Methods:Both bioinformatics tools and quantitative real time polymerase chain reaction (RT-PCR) were used to examine the expression of IL-6 in cancer cells. To map super-enhancers of IL-6, sgRNAs were constructed. Stable knockout cells were established and subsequently used for cell proliferation and colony formation assay. The correlation between mapped super-enhancers and IL-6 expression was studied by ATAC-seq analysis.Results: The expression of IL-6 was high in multiple cancers, including pancreatic cancer (PAAD).The elevated expression of IL-6 in PAAD was further confirmed by transcriptional data and in a panel of pancreatic cancer cell lines (one immortal HPDE6-C7 cell line and four PDAC cell lines: BxPC-3, PANC-1, AsPC-1 and CFPAC-1). When treated with JQ-1 and I-BET-762, two inhibitors of super-enhancers, the expression of IL-6 in multiple cancer cells including CFPAC-1, HeLa and SUM-159 cells was significantly reduced. By analyzing the H3K27Ac profiling, BRD4 binding, Med1 binding and DNA conservation in CFPAC-1, HeLa and SUM-159 cells, we identified a potential super-enhancer (IL6-SE) that might be important for IL-6 expression in cancer. The super-enhancer (IL6-SE) can be further divided into two elements (IL6-SEa and IL6-SEb). Genetic deletion of IL6-SEa in cancer cells greatly reduces the expression of IL-6. IL6-SEa deficient cells also showed low proliferation and colony formation ability. In patients, the epigenetic activation (ATAC signal) of IL6-SEa is correlated with the expression of IL-6.Conclusions: In summary, we not only provide convincing experimental evidence to demonstrate that IL-6 expression in cancer is dependent on super-enhancers but also identified IL6-SEa as a critical DNA regulatory element. Our findings provide new insights to understand the epigenetic regulation of IL-6 expression in cancers.

Mutant TP53 switches therapeutic vulnerability during gastric cancer progression within Interleukin-6 family cytokines

“…On the other hand, loss of TP53 protein is likely to release its transcriptional repressor activity on the IL6 promoter. Meanwhile, the TP53 R172H protein has recently been shown to induce expression of the CSF1 cytokine via an interaction with BRD4 on a histone 3 lysine 27 acetylation-rich (H3K27ac) region 49 , which is also found in a super-enhancer in the IL6 locus that is susceptible to BRD4-inhibition 50 . Indeed, epigenetic activation of this superenhancer, as judged by ATAC sequencing signals, correlated with IL6 expression in esophageal and pancreatic cancer patients.…”

The Emerging Role of Super-enhancers as Therapeutic Targets in The Digestive System Tumors

“…Interleukin-6 (IL-6) is overexpressed in pancreatic cancer. Bao et al demonstrated that genetic deletion of IL6-SEa or treatment with two inhibitors of the SE-related BET protein, JQ-1 and I-BET762, significantly reduced the IL-6 expression levels in multiple cancer cells [54].…”